Additive manufacturing typically involves the production of three-dimensional parts by depositing material layer by layer to build either complete components or add features to a pre-formed substrate. It contrasts with conventional subtractive machining processes, in that a component produced by an additive manufacturing process is near net shape, i.e. it is close to its final (net) shape thereby reducing the need for additional finishing and wasted excess material.
A key challenge with additive manufacturing processes, particularly for the production of larger components, is the distortion of the manufactured part during the deposition process due to the high internal stresses generated as the deposited material solidifies.
A solution to this problem is presented in WO2014/072699. A bed supports a parent plate of a work piece which is held in position by clamps. A stack of layers is built on the parent plate by a process of additive manufacturing, and stresses in the work piece are measured by load cells while progressively forming the stack. If such stresses are above a predetermined threshold, the work piece is stress relieved by a cold working process such as cold rolling or peening while mounted to the additive manufacturing apparatus.